22,332 research outputs found
Optimal experiment design in a filtering context with application to sampled network data
We examine the problem of optimal design in the context of filtering multiple
random walks. Specifically, we define the steady state E-optimal design
criterion and show that the underlying optimization problem leads to a second
order cone program. The developed methodology is applied to tracking network
flow volumes using sampled data, where the design variable corresponds to
controlling the sampling rate. The optimal design is numerically compared to a
myopic and a naive strategy. Finally, we relate our work to the general problem
of steady state optimal design for state space models.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS283 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Malware Detection Module using Machine Learning Algorithms to Assist in Centralized Security in Enterprise Networks
Malicious software is abundant in a world of innumerable computer users, who
are constantly faced with these threats from various sources like the internet,
local networks and portable drives. Malware is potentially low to high risk and
can cause systems to function incorrectly, steal data and even crash. Malware
may be executable or system library files in the form of viruses, worms,
Trojans, all aimed at breaching the security of the system and compromising
user privacy. Typically, anti-virus software is based on a signature definition
system which keeps updating from the internet and thus keeping track of known
viruses. While this may be sufficient for home-users, a security risk from a
new virus could threaten an entire enterprise network. This paper proposes a
new and more sophisticated antivirus engine that can not only scan files, but
also build knowledge and detect files as potential viruses. This is done by
extracting system API calls made by various normal and harmful executable, and
using machine learning algorithms to classify and hence, rank files on a scale
of security risk. While such a system is processor heavy, it is very effective
when used centrally to protect an enterprise network which maybe more prone to
such threats.Comment: 6 page
Phase Space dynamics of triaxial collapse: Joint density-velocity evolution
We investigate the dynamics of triaxial collapse in terms of eigenvalues of
the deformation tensor, the velocity derivative tensor and the gravity Hessian.
Using the Bond-Myers model of ellipsoidal collapse, we derive a new set of
equations for the nine eigenvalues and examine their dynamics in phase space.
The main advantage of this form is that it eliminates the complicated elliptic
integrals that appear in the axes evolution equations and is more natural way
to understand the interplay between the perturbations.
This paper focuses on the density-velocity dynamics. The Zeldovich
approximation implies that the three tensors are proportional; the
proportionality constant is set by demanding `no decaying modes'. We extend
this condition into the non-linear regime and find that the eigenvalues of the
gravity Hessian and the velocity derivative tensor are related as , where the triaxiality parameter . This is a {\it new universal relation} holding true
over all redshifts and a range of mass scales to within a few percent accuracy.
The mean density-velocity divergence relation at late times is close to linear,
indicating that the dynamics is dictated by collapse along the largest
eigendirection. This relation has a scatter, which we show, is intimately
connected to the velocity shear. Finally, as an application, we compute the
PDFs of the two variables and compare with other forms in the literature.Comment: 23 pages (16 text+appendix); 11 figures, revised version accepted for
publication in MNRA
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